Sir Peter Jackson 'amazed' by quality of restored WWI footage that's become his new documentary

Kiwi director Sir Peter Jackson has been busy bringing rare original World War One footage to life.

Sir Peter is putting the final touches on his new documentary They Shall Not Grow Old which turns ordinary real-life soldiers into stars of a film marking the centenary of Armistice Day.

TVNZ1's Seven Sharp sent 1 NEWS Europe Correspondent Joy Reid to meet him ahead of the film's premiere in London and get a sneak peek at what's in store.

Featuring real soldiers, their real emotion and real shellfire, the film is WWI as you've never seen it before.

"The result is just, to me, I was amazed. It was so much better than what I thought. When I originally thought, 'I wonder how well we can restore film,' I didn't think we could restore it that well," Sir Peter said.

Sir Peter, who has long had a fascination with the Great War, together with his Wellington-based digital whizkids, have spent the past few years transforming grainy, jerky 100-year-old black and white vision into high-quality colour.

"Just imagine Charlie Chaplain sped up film. You've got to deal with scratches, you've got to deal with grain, you've got to deal with the fact that after 100 years the film has shrunk. Some of it's black and dark, some of it's really over exposed, it's all over the show. So you just  want to make it look like normal film," Sir Peter said. 

"People have colourised black and white film before but I don't think they've ever spent the time that we did and the detail that we put into it to get it as good as you can.

"The other part of it is the audio where we had access to over 600 hours of original recordings of veterans.

"We wanted them to be the only voices that are really heard. We wanted the veterans to tell their own story. It really just told us that it's got to be colour because these guys are seeing the war in colour, they're not seeing it black and white.

He introduced not just a world of colour to the footage but also sound. Forensic lip readers deciphered the soldiers' banter and actors revoiced it.

And the live firing sounds were specially recreated by the New Zealand Army.

"What did surprise me listening to all the veterans' tapes was was how little self pity they had for themselves," Sir Peter said.